Relative abundance - comparison between the isotopes Percent abundance -
comparing the totals.
relative abundance:the number of organisms of a particular kind as a percentage of the total number of organisms of a given area or community; the number of birds of a particular species as a percentage of the total bird population of a given area percent:figured or expressed on the basis of a rate or proportion per hundred (used in combination with a number in expressing rates of interest, proportions, etc.